Well, this is all a bit embarrassing.
Yesterday our youngest son logged on to the windows 7 lap top remotely. One of the first things he tried was to run the unpacked set-up file in ss/English as administrator. Sonicstage installed OK. Did the same thing on the Vista desktop and that worked OK. Am sure that this was tried a good while ago. Will now stop fiddling.
However, all's well that ends well. Many thanks to inquisitor and kalkie for the many suggestions.